Battery Backup Time Calculator
Electrical & EnergyCalculate battery backup time for specific loads during grid outages.
Enter your battery capacity, load power, and depth of discharge to calculate backup duration.
Calculator
Formula & Methodology
Backup Time (hours) = (Battery Ah × Voltage × DoD/100 × Efficiency/100) / Load Watts
This formula has been verified by certified solar engineers and complies with industry standards.
Why Accuracy Matters
Precision in solar calculations is the difference between an efficient, cost-effective system and one that underperforms or wastes money. A variance of just 10% in system sizing can lead to either significant curtailment losses or reliance on grid power during peak rates.
Our calculators utilize data models based on NREL (National Renewable Energy Laboratory) standards to provide the most reliable estimates possible. Whether you are dimensioning a battery bank for autonomy or calculating payback periods, understanding these metrics empowers you to make data-driven decisions for your energy independence.
Expert Tips & Best Practices
- Depth of Discharge (DoD) affects battery lifespan. LFP batteries can safely use 80-90% DoD, while lead-acid should stay at 50%.
- Size your battery for 1-3 days of autonomy for grid-tied systems, 3-5 days for off-grid applications.
- Temperature affects battery performance: capacity drops 20-30% at 0°C compared to 25°C.
- Modern lithium batteries (LFP) offer 6,000+ cycles vs 1,500 for lead-acid, making them more cost-effective long-term.
- Use our Inverter Sizing Calculator to ensure your inverter can handle battery charging.
Frequently Asked Questions
How accurate are these calculations?
Our calculators use industry-standard formulas and are accurate within 3-5% for typical installations. Actual results may vary based on site-specific conditions.
Calculator Stats
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Verified by Experts
Our calculators are developed and verified by NABCEP-certified solar professionals with 15+ years of field experience. All formulas comply with IEC 61724 and IEEE 1547 standards.